题目

根据对话内容，用所给单词的恰当形式填空。 forget , crowded , prevent , needn’t , build A：Welcome to our school , Dr . King.B：Thank you. A：Could you give us some suggestions to  1  the flu?B：Sure. First , doing sports much can  2  us up.A：Must we clean our rooms every day?B：No, you  3  . But it’s necessary to keep the air fresh.A：What should we do then?B：Don’t  4  to wash hands before meals.A：That’s fine. B：And you had better keep away from  5  places.  A：Thanks for your advice.19．金属活动性顺序在工农业生产和科学研究中有重要应用，它可以给你提供一些判断依据．例如：在金属活动性顺序里，位于氢前面的金属能置换出盐酸、稀硫酸中的氢．这里的“氢”指的是（　　）A．氢气B．氢原子C．氢离子D．氢元素